diff --git a/ch04.asciidoc b/ch04.asciidoc
index 6e2524a4..1a1a6dbc 100644
--- a/ch04.asciidoc
+++ b/ch04.asciidoc
@@ -213,7 +213,7 @@ image::images/msbt_0404.png["ecc_illustrated"]
 
 [TIP]
 ====
-Most bitcoin implementations use the((("OpenSSL cryptographic library"))) OpenSSL cryptographic library to do the elliptic curve math. For example, to derive the public key, the function((("EC_POINT_mul() function (OpenSSL)"))) +EC_POINT_mul()+ is used. See http://wiki.openssl.org/index.php/Elliptic_Curve_Cryptography. (((range="endofrange", startref="ix_ch04-asciidoc7")))(((range="endofrange", startref="ix_ch04-asciidoc6")))(((range="endofrange", startref="ix_ch04-asciidoc0")))
+Most bitcoin implementations use the((("OpenSSL cryptographic library"))) OpenSSL cryptographic library to do the elliptic curve math. For example, to derive the public key, the function((("EC_POINT_mul() function (OpenSSL)"))) +EC_POINT_mul()+ is used. See http://bit.ly/1ql7bn8[OpenSSL]. (((range="endofrange", startref="ix_ch04-asciidoc7")))(((range="endofrange", startref="ix_ch04-asciidoc6")))(((range="endofrange", startref="ix_ch04-asciidoc0")))
 ====
 
 === Bitcoin Addresses